bonjour mm43!
Diagnostics - Self test, Output voltage, Output current, Operating hours, Temperatures, Power.
Was the BC-1300 LithIon specific? From the literature, the LithIon pack, whether pouch, prism or roll, does not tolerate intrusion into its Cathode, Separator, Anode stack. Even the slightest foreign object will cause a focal "shutdown" and compromise the useful life.
I have no doubt there are diagnostics and storage. The Battery install, however, suggests the only wiring external to the case is +/- conductors, and Ground. Would the diagnostics storage be co-located with the PCBs? Inside the case?
many thanks